Research

Rivers are conduits for transport of fresh water, sediment and nutrients throughout the landscape. At the same time, rivers are vital pathways for the migration of aquatic species, such as salmon. My research focuses on understanding how rivers respond to changes, ranging from long-term variations in tectonics or climate to short-term shifts in management style or land use. I link measurements of channel morphology from high-resolution airborne lidar digital elevation models with field-based measurements of stream processes.

New England lakes project

This is a collaboration with Tim Cook from UMass-Amherst, funded in 2018-19 by the Bullard Fellowship at Harvard Forest. The landscape formerly occupied by the Laurentide ice sheet contains thousands of natural lakes that have been accumulating sediment since deglaciation 10-15 thousand years ago. We use these records to study the sensitivity of the landscape to disturbances, such as floods, landslides, forest fires and land clearance. We measure spatial and temporal variations in sediment yields from the early-middle Holocene through the present day by developing continuous records of sediment accumulation and event deposition in lakes throughout New England and New York. We collect sediment cores from lakes sensitive to the deposition of terrestrial sediment and the preservation of event deposits. We use high resolution digital elevation models, geologic maps, and aerial photographs to quantify watershed geomorphologic and hydrologic history and processes, and evaluate geomorphic controls on erosion. Our goal is to understand how land-use history, climate change, and glacial geology control erosion rates and sediment yields in our intensively lived-in landscape.

Publications: New England lakes project

Cook, T.L., Snyder, N.P., Oswald, W.W. and Paradis, K., 2020, Timber harvest and flood impacts on sediment yield in a postglacial, mixed-forest watershed, Maine, USA, Anthropocene, v. 29, https://doi.org/10.1016/j.ancene.2019.100232.

Cook, T.L. and Snyder, N.P., 2021, Web Extras: Exploring the Intersection of Climate Change and Land Use, Northern Woodlands, February 2021.

Anthropocene streams project

Starting in 2015, this is a collaborative project with Dorothy Merritts and Bob Walter from Franklin and Marshall College, funded by the National Science Foundation. Recent global sedimentation studies demonstrate that rates of erosion due to human activities exceed the amount of sediment delivered to the oceans by rivers. At the same time, field-based studies at the channel to watershed scale have found large quantities of sediment stored in valley bottoms during the past few centuries. This project will bridge the gap between global and watershed-based approaches by quantifying the amount of Anthropocene (recent, human related) sediment stored in valley bottoms of the northeastern United States, and then comparing this amount to published volumes and timescales of (1) erosion from the landscape, and (2) deposition in reservoirs, lakes, and estuaries along the Atlantic margin. The research will use high-resolution topographic data to map the extent and thickness of this fill over large spatial areas (1,000-10,000 square km), and will test these methods using fieldwork (mapping, coring, geophysical data collection, sediment sampling and dating) in key watersheds. A central goal is to evaluate the extent to which sediment storage in the unglaciated mid-Atlantic region applies in the glaciated, less-studied New England region, where upland soils are thin, sediment sources are generally localized to glacial deposits, and large natural lakes and wetlands provide terrestrial accommodation space. The results of the project will help resolve the discrepancy between erosion and deposition rates at small spatial (watershed) and temporal (decadal to centennial) scales versus the rates that occur globally and over geological time.

Publications: Anthropocene streams project (see also)

Dow, S.*, Snyder, N.P., Ouimet, W.B., Martini, A.M., Yellen, B., Woodruff, J.D., Newton, R.M., Merritts, D.J., and Walter, R.C., 2020, Estimating the timescale of fluvial response to anthropogenic disturbance using two generations of dams on the South River, Massachusetts, USA, Earth Surface Processes and Landforms, https://doi.org/10.1002/esp.4886.

Johnson, K.M.*, Snyder, N.P., Castle, S.*, Hopkins, A.J.*, Waltner, M.*, Merritts, D.J., and Walter, R.C., 2019, Legacy sediment storage in New England river valleys: Anthropogenic processes in a postglacial landscape, Geomorphology, v. 327, p. 417-437, https://doi.org/10.1016/j.geomorph.2018.11.017.

Hopkins, A.J.*, and Snyder, N.P., 2016, Performance evaluation of three DEM-based fluvial terrace mapping methods, Earth Surface Processes and Landforms, v. 41, n. 8, p. 1144-1152, https://doi.org/10.1002/esp.3922.

(*BC student co-authors.)

Effects of dams and dam removal

Dams represent important breaks in the continuum of fluvial processes as they alter the flow of sediment, wood and water. Dams also present society with important environmental decisions because of their benefits (e.g., power generation, water storage, flood control) and costs (e.g., potential failure, maintenance costs, barrier to migrating aquatic species, changes in river habitats). Throughout the U.S., communities are making the decision to remove dams because they believe the costs exceed the benefits. This shift in river management motivates new research, both to aid in future decisions and to gain fundamental insight into watershed processes. Since 2007, my students and I have studied sediment dynamics associated with the removal of the Merrimack Village Dam on the Souhegan River in southern New Hampshire. Dam removals provide opportunities to study large-magnitude channel changes over short intervals. Further, historical sedimentation behind dams may persist in the landscape for a long time after dams are removed. Previously, I studied reservoir sedimentation rates and processes behind Englebright Dam on the Yuba River in northern California.

Publications: Dams and dam removal

Lisius, G.L.*, Snyder, N.P., and Collins, M.J., 2018, Vegetation community response to hydrologic and geomorphic changes following dam removal, River Research and Applications, v. 34, n. 4, p. 317-327, https://doi.org/10.1002/rra.3261.

Collins, M.J., Snyder, N.P., Boardman, G., Banks, W.S.L., Andrews, M., Baker, M.E., Conlon, M.*, Gellis, A., McClain, S., Miller, A., and Wilcock, P., 2017, Channel response to sediment release: insights from a paired analysis of dam removal, Earth Surface Processes and Landforms, https://doi.org/10.1002/esp.4108.

Santaniello, D.J.*, Snyder, N.P., and Gontz, A.M., 2013, Using ground-penetrating radar to determine the quantity of sediment stored behind the Merrimack Village Dam, Souhegan River, New Hampshire, in DeGraff, J.V. and Evans, J.E. (editors), The Challenges of Dam Removal and River Restoration, GSA Reviews in Engineering Geology, v. XXI, p. 45-57, https://doi.org/10.1130/2013.4021(04).

Pearson, A.J.*, Snyder, N.P., and Collins, M.J., 2011, River response to dam removal: the Souhegan River and the Merrimack Village Dam, Merrimack, New Hampshire, Water Resources Research, v. 47, https://doi.org/10.1029/2010WR009733.

Snyder, N.P., Wright, S.A., Alpers, C.N., Flint, L.E., Holmes, C.W., and Rubin, D.M, 2006, Reconstructing depositional processes and history from reservoir stratigraphy: Englebright Lake, Yuba River, northern California, Journal of Geophysical Research, v. 111, F04003, https://doi.org/10.1029/2005JF000451.

Alpers, C.N., Hunerlach, M.P., Marvin-DiPasquale, M.C., Antweiler, R.C., Lasorsa, B.K., De Wild, J.F., and Snyder, N.P., 2006, Geochemical data for mercury, methylmercury, and other constituents in sediments from Englebright Lake, California, 2002, U.S Geological Survey Data-Series Report 2005-151, http://pubs.water.usgs.gov/ds151/, 95 p.

Curtis, J.A., Flint, L.E., Alpers, C.N., Wright, S.A., and Snyder, N.P., 2006, Use of Sediment Rating Curves and Optical Backscatter Data to Characterize Sediment Transport in the Upper Yuba River Watershed, California, 2001–03, U.S. Geological Survey Scientific Investigations Report 2005-5246, http://pubs.usgs.gov/sir/2005/5246/, 74 p.

Snyder, N.P., Rubin, D.M., Alpers, C.N., Childs, J.R., Curtis, J.A., Flint, L.E., and Wright, S.A., 2004, Estimating rates and properties of sediment accumulation behind a dam: Englebright Lake, Yuba River, northern California, Water Resources Research, v. 40, W11301, https://doi.org/10.1029/2004WR003279.

Snyder, N.P. , Allen, J.R., Dare, C., Hampton, M.A., Schneider, G., Wooley, R.J., Alpers, C.N., and Marvin-DiPasquale M.C., 2004, Sediment grain-size and loss-on-ignition analyses from 2002 Englebright Lake coring and sampling campaigns, U.S. Geological Survey Open-File Report 2004-1080, http://pubs.usgs.gov/of/2004/1080/, 46 p.

Snyder, N.P. , Alpers, C.N., Flint, L.E., Curtis, J.A., Hampton, M.A., Haskell, B.J., and Nielson, D.L., 2004, Report on the May-June 2002 Englebright Lake deep coring campaign, U.S. Geological Survey Open-File Report 2004-1061, http://pubs.usgs.gov/of/2004/1061/, 32 p., 10 plates.

Snyder, N.P. , and Hampton, M.A., 2003, Preliminary cross section of Englebright Lake sediments, U.S. Geological Survey Open-File Report 03-397, http://geopubs.wr.usgs.gov/open-file/of03-397/, 1 plate.

Childs, J.R., Snyder, N.P., Hampton, M.A., 2003, Bathymetric and geophysical surveys of Englebright Lake, Yuba-Nevada Counties, California, U.S. Geological Survey Open-File Report 03-383, http://geopubs.wr.usgs.gov/open-file/of03-383/, 20 p.

(*BC student co-authors.)

Links: Dams and dam removal

Nashua Telegraph articles about the Souhegan River dam removal: August 22, 2008; August 29, 2008; May 7, 2009.

Controls on the morphology of rivers in response to deglaciation and land-use change

The New England landscape is rich with opportunities for studying geomorphic responses to changes in external forces. The region hosts a large human population and has undergone large-scale climate (late Pleistocene continental glaciation, Holocene transgression), geodynamic (post-glacial isostatic rebound) and land-use (deforestation and reforestation) changes. The challenge is studying fluvial processes in a landscape where relief and sediment supply bear the strong imprint of continental glaciation. For this research, my students and I link measurements from high-resolution lidar digital elevation models with field measurements. From 2007 to 2013, this work was funded by a National Science Foundation award for a project entitled CAREER: Land use, geologic and climatic controls on stream processes in northern New England using airborne laser swath mapping, from the Geomorphology and Land Use Dynamics program. That project focused on understanding the interrelated issues associated with Atlantic salmon habitat requirements, river restoration, and trajectories of channel change in northern New England.

Publications: Controls on New England river morphology

Waldman, J., Wilson, K.A., Mather, M., and Snyder, N.P., 2016, A resilience approach can improve anadromous fish restoration, Fisheries, v. 41, n. 3, p. 116-126, https://doi.org/10.1080/03632415.2015.1134501.

Bresney, S.R.*, Moseman-Valtierra, S., and Snyder, N.P., 2015, Observations of greenhouse gases and nitrate concentrations in a Maine river and fringing wetland, Northeastern Naturalist, v. 22, n. 1, p. 120-143, https://doi.org/10.1656/045.022.0125.

Armstrong, W.H., Collins, M.J., and Snyder, N.P., 2014, Hydroclimatic flood trends in the northeastern United States and linkages with large-scale atmospheric circulation patterns, Hydrological Sciences Journal, v. 59, p. 1636-1655, https://doi.org/10.1080/02626667.2013.862339.

Kasprak, A., Magilligan, F.J., Nislow, K.H., Renshaw, C.E., Snyder, N.P., and Dade, W.B., 2013, Differentiating the relative importance of land cover change and geomorphic processes on fine sediment sequestration in a logged watershed, Geomorphology, v. 185, p. 67-77, https://doi.org/10.1016/j.geomorph.2012.12.005.

Snyder, N.P., Nesheim, A.O.*, Wilkins, B.C.*, and Edmonds, D.A., 2013, Predicting grain size in gravel-bedded rivers using digital elevation models: application to three Maine watersheds, Geological Society of America Bulletin, v. 125, n. 1/2, p. 148-163, https://doi.org/10.1130/B30694.1.

Armstrong, W.H.*, Collins, M.J., and Snyder, N.P., 2012, Increased frequency of low magnitude floods in New England, Journal of the American Water Resources Association, v. 48, n. 2, p. 306-320, https://doi.org/10.1111 ⁄ j.1752-1688.2011.00613.x.

Kasprak, A., Magilligan, F.J., Nislow, K.H., and Snyder, N.P., 2012, A lidar-derived evaluation of watershed-scale large woody debris sources and recruitment mechanisms: coastal Maine, USA, River Research and Applications, published online, https://doi.org/10.1002/rra.1532.

Snyder, N.P., 2012, Restoring geomorphic resilience in streams, in Church, M., Biron, P.M., and Roy, A., editors, Gravel-bed Rivers: Processes, Tools, Environments, John Wiley and Sons, Ltd., p. 160-164, https://doi.org/10.1002/9781119952497.ch14.

Wilkins, B.C.*, and Snyder, N.P., 2011, Geomorphic comparison of two Atlantic coastal rivers: toward an understanding of physical controls on Atlantic salmon habitat, River Research and Applications, v. 27, n. 2, p. 135-156, https://doi.org/10.1029/2009EO060001.

Snyder, N.P. , 2009, Studying stream morphology with airborne laser elevation data, Eos, Transactions, American Geophysical Union, v. 90, n. 6, p.45-46, https://doi.org/10.1029/2009EO060001.

Snyder, N.P., Castele, M.R.*, and Wright, J.R., 2009, Bedload entrainment in low-gradient paraglacial coastal rivers of Maine, U.S.A.: Implications for habitat restoration, Geomorphology, v. 103, n. 3,p. 430-446, https://doi.org/10.1016/j.geomorph.2008.07.013.

(*BC student co-authors.)

Links: Controls on New England river morphology

JAWRA editor's blog post on Armstrong et al. (2012): March 12, 2012.

BC Chronicle article about lidar mapping and Eos article: February 26, 2009. Other articles: EurekAlert; ScienceDaily.

BC Chronicle article about NSF CAREER award: March 15, 2007.

Previous research

Publications: Death Valley area

Snyder, N.P., and Kammer, L.L.*, 2008, Dynamic adjustments in channel width in response to a forced diversion: Gower Gulch, Death Valley National Park, California, Geology, v. 25, p. 187-190, https://doi.org/10.1130/G24217A.1.

Snyder, N.P., and Hodges, K.V., 2000, Depositional and tectonic evolution of a supradetachment basin: 40Ar/ 39Ar geochronology of the Nova Formation, Panamint Range, California, Basin Research, v. 12, n. 1, p. 19-30, https://doi.org/10.1046/j.1365-2117.2000.00108.x.

(*BC student co-authors.)

Links: Death Valley area

BC Magazine article about Death Valley research: Spring 2008.

Other articles about Death Valley research: EurekAlert; PhysOrg; ScienceDaily.

Publications: Channel response to tectonics, bedrock erosion processes, digital elevation model analysis

Moon, S., Merritts, D.J., Snyder, N.P., Bierman, P., Sanquini, A., Fosdick, J.C., and Hilley, G.E., 2018, Erosion of coastal drainages in the Mendocino Triple Junction region (MTJ), northern California, Earth and Planetary Science Letters, v. 502, p. 156-165, https://doi.org/10.1016/j.epsl.2018.09.006.

Wobus, C.W., Whipple, K.X, Kirby, E., Snyder, N.P., Johnson, J., Spyropolou, K., Crosby, B., and Sheehan, D., 2006, Tectonics from topography: Procedures, promise, and pitfalls, in Willett, S.D., Hovius, N., Brandon, M.T., and Fisher, D.M., editors, Tectonics, Climate, and Landscape Evolution, Geological Society of America Special Paper 398, p. 55-74, https://doi.org/10.1130/2006.2398(04).

Snyder, N.P., Whipple, K.X., Tucker, G.E., and Merritts, D.J., 2003, Importance of a stochastic distribution of floods and erosion thresholds in the bedrock river incision problem, Journal of Geophysical Research, v. 108 (B2), 2117, https://doi.org/10.1029/2001JB001655. correction

Snyder, N.P., Whipple, K.X., Tucker, G.E., and Merritts, D.J., 2003, Channel response to tectonic forcing: analysis of stream morphology and hydrology in the Mendocino triple junction region, northern California, Geomorphology, v. 53, p. 97-127, https://doi.org/10.1016/S0169-555X(02)00349-5.

Snyder, N.P., Whipple, K.X., Tucker, G.E., and Merritts, D.J, 2002, Interactions between onshore bedrock-channel incision and nearshore wave-base erosion forced by eustasy and tectonics, Basin Research, v. 14, p. 105-127, https://doi.org/10.1046/j.1365-2117.2002.00169.x.

Snyder, N.P., Whipple, K.X., Tucker, G.E., and Merritts, D.J, 2000, Landscape response to tectonic forcing: digital elevation model analysis of stream profiles in the Mendocino triple junction region, northern California, Geological Society of America Bulletin, v. 112, n. 8, p. 1250-1263, https://doi.org/10.1130/0016-7606(2000)112<1250:LRTTFD>2.0.CO;2.

Whipple, K.X., Snyder, N.P., and Dollenmayer, K., 2000, Rates and processes of bedrock incision by the Upper Ukak River since the 1912 Novarupta ash flow in the Valley of Ten Thousand Smokes, Alaska, Geology, v. 28, n. 9, p. 835-838, https://doi.org/10.1130/0091‑7613(2000)28<835:RAPOBI>2.0.CO;2.